This invention relates to a new and improved rotary pump for use in many diverse pumping applications, especially in any situation where it would be advantageous to be able to replace or dispose of certain components of the pumping mechanism that have expended their useful lives without having to also dispose of other parts that have additional useful life and/or are more expensive to replace. These concerns are especially relevant in applications employing magnets, which are relatively expensive, as the means of driving the rotation of the pump.
The art is replete with examples of rotary pump mechanisms employing various means for driving the rotation of the pump, including but not limited to magnets, gears, electrical conduction and induction, belts and rollers. Pumps employing magnetic driving systems are exemplified by U.S. Pat. Nos. 3,647,324 and 4,037,984 of which Applicant is an inventor. These references disclose pumps for use with biological fluids, especially blood. These pumps are especially useful in heart-lung machines and devices for assisting ailing heart muscles. The pumps are comprised of a housing in which an impeller and a magnet are incorporated. The magnet is magnetically connected to a second magnet outside of the housing. The second magnet is in turn connected to a motor. When the motor rotates the second magnet, the first magnet also rotates, turning the impeller with it.
Other pumps incorporating similar magnetic driving mechanisms are represented by U.S. Pat. Nos. 3,306,221, 3,321,081, 3,575,536, 4,135,253 and 4,165,206.
These magnetic systems keep the pumped fluid separated from the mechanical driving elements of the pump, for example the motor. This feature provides the advantages of (1) preventing fluids from contacting the driving mechanism, thus preventing corrosion, electrical shorts, seizing and other undesirable results that render the driving mechanism useless; (2) preventing lubricants, detritus and other foreign material from contacting the fluid being pumped, especially when the fluid is blood; and (3) preventing the fluid being pumped from contacting air, especially when the fluid is blood.
To maintain separation between the fluid and the driving mechanism, many devices in the prior art incorporate an expensive driving mechanism, for example magnet-driven shafts or other rotatable components, into the impeller section of the pumping device. Since components associated with rotation are usually the mechanical elements that wear out most quickly, replacement of these components means replacement of the entire impeller section including components in that section which may not have outlived their useful lives. Alternatively, in some applications, especially those in the medical field where the pump is used in contact with bodily fluid or preparations of body tissues, it may be necessary to dispose of the impeller section of a pump because it cannot be reused due to the possibility of contamination or other undesirable reaction between substances from one patient and those of another. With pumps of the prior art, if the impeller and other elements contacting the biological fluid must be discarded, other components, including parts of the magnetic or other driving mechanism, must be unnecessarily discarded with the impeller. The unnecessary, inefficient and uneconomical loss of components that would still be useful is a problem that is common to many rotary pumping devices in the prior art.
It would be desirable, therefore, to provide a rotary pump that keeps fluid away from the driving mechanism, yet allows replacement or disposal of components of the pump which cannot be reused or continue to be used, without also disposing of components that are still useful.